1. Field of the Art
This invention relates to processes for preparing polymeric compositions having improved anti-static properties. More particularly, this invention relates to a process for preparing such polymeric compositions in which metal salts and/or oxides having reduced resistivities are introduced into a polymer in or on its surface.
2. Description of the Prior Art
Normally dry polymeric compositions have high resistivities. For example a well known polyamide, polycaprolactam, has a resistivity of about 10.sup.15 ohm cm. As result when such compositions are employed in the construction of articles, such as fibers, wall coverings, articles of furnishings, and other textile articles, such articles tend to accumulate static electricity.
Several methods have been proposed in the prior art for rendering articles conductive, and thereby improving their anti-static properties. One simple method of making such articles conductive consists of incorporating metal or graphite fibers into bundles with fibers composed of a polymeric composition. This method however, provides several adverse effects. For example, articles composed of such bicomponent bundles do not dye as uniformly as would be expected of an article composed of only polymer fibers. Moreover, only the metal or graphite fibers are conductive, as a result, if the article is employed as a heating surface, the heat is not liberated at all points of the article and remains localized around the metal or graphite wires.
In another method disclosed in French Pat. No. 644,429, fibrous materials are rendered more conductive by metallization. In this process, the materials are immersed in a cuproammonium bath to which silver nitrate has been added, followed by immersion in a coagulation bath. The material is then treated with hydrogen sulfide and with an electrolyte bath. At least one prior art reference has indicated that this process is not fully satisfactory because the numerous process steps required, make it an expensive process.
In another such process described in U.S. Pat. No. 3,940,533, an article is exposed to hydrogen sulfide at superatmospheric pressure or treated with an aqueous bath of thioacetamide or thiourea, and is then immersed in an aqueous solution of a copper, silver, tin, lead or mercury salt. As a result of such treatment, the salt reacts with the hydrogen sulfide to form an electrically conductive metal deposit on the article. In U.S. Pat. No. 3,983,286, it discloses that the adhesion of the salt applied by the above identified procedure can be improved by carrying out the immersion step in the presence of a polyphenol.